Excessively High Idle / '88 XLT / 5.8 EFI
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Junior User
Joined: Jun 2001
Posts: 69
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From: Florida
Excessively High Idle / '88 XLT / 5.8 EFI
Need help! My '88 Bronco XLT 5.8 EFI normally would crank right up ... fast idle at around 1300 rpm for about a minute or so, then idle down to 850 rpm in neutral. Lately, it fast idles at 1300 when started ... then the engine speed gradually increases up to about 2200 rpm. Can not get engine idle speed to drop by tapping the gas pedal. If I place the auto tranny in gear and operate the truck for 15 minutes or so, the engine idle speed will then drop to a normal 750 rpm. Engine runs great otherwise ... have cleaned out the IAC valve chamber in the throttle body. Can anyone who experienced a similar problem help me out ... thanks, John
Senior User
Joined: Feb 2002
Posts: 258
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From: Allegan Michigan
Excessively High Idle / '88 XLT / 5.8 EFI
I hade the same symptoms on my 89 F250 5.8 My best guess is the throttle position sensor. Not really a big thing to replace and cost's about $35.00. If this is bad the truck will suck more fuel also.
Good Luck.
Cyberbyrd
Good Luck.
Cyberbyrd
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Junior User
Joined: Jun 2001
Posts: 69
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From: Florida
Excessively High Idle / '88 XLT / 5.8 EFI
Cyberbyrd, "right on" I replaced the TPS sensor as you suggested and it corrected the problem immediately. Suprisingly, an identical replacement part cost only $23.99 at a local Autozone store. Had to remove the throttle body to access the two phillips head screws on the sensor, but not a big deal labor-wise. Many thanks to you for your advice on solving my problem ... John 
